Revert "[PGO] Profile summary reader/writer support"
Revert "[PGO] Profile summary reader/writer support"

This reverts commit 6db0594cf21962d6dbba3c6b139f3641636fb3e8.

Note: This was merged twice, and will cause a build failure. The
previous (correct) merge is here:

3ae83b9b03e2690dad96b7146d533e88d8c10cac

apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm